Copper electrodeposition electrolytes and method

ABSTRACT

IMPROVED ELECTRODEPOSITION OF COPPER IS ACHIEVED BY ADDING A COMBINATION OF A CATION ACTIVE ORGANIC NITROGEN COMPOUND AND A LIGNOSULFONATE MATERIAL TO A COPPER ELECTRODEPOSITION ELECTROLYTE.

United States Patent US. Cl. 20452 R Claims ABSTRACT OF THE DISCLOSUREImproved electrodeposition of copper is achieved by adding a combinationof a cation active organic nitrogen compound and a lignosulfonatematerial to a copper electrodeposition electrolyte.

The present invention relates to electrolytic deposition of copper fromacid electrolytes. More particularly, this invention relates to new andimproved electrolytes for use in the electrorefining of copper whichwill promote smoother and more efiicient plating and to new and improvedadditive agents to be introduced therein.

In the electrolytic refining of copper, purified cathode copper isobtained by passing an electric current from an impure copper anodethrough an aqueous acid electrolyte to a pure copper cathode. The copperdissolves from the anode and is deposited on the cathode in purifiedform. However, it has been found to be highly advantageous to introduceadditives into the electrolyte in order to promote the formation of asmoth, dense deposit of copper on the cathode. Without these additiveagents, the copper deposits on the cathode are soft, coarselycrystalline and prone to develop into nodules or trees. Since thespacing between the anode and the cathode is usually on the order of oneto two inches, these nodules of copper can grow from the cathode to theanode and cause a short circuit. Even if a short circuit does notdevelop, a rough cathode deposit will cause entrainment of electrolytesin the cathode which cannot be washed out and remains as a contaminant.

Many such electrolyte additive agents have been employed in attemptingto prevent the nodules or trees from forming on the cathode surface.Some of these known additive agents have, in fact, improved thecharacter of the cathode deposit to a limited extent. But, the problemhas not been solved heretofore.

It is, therefore, an object of the present invention to provide new andimproved copper electrodeposition electrolytes which produce copperelectrodeposits which are smooth, dense and essentially free ofprotrusions.

Another object is to provide new and improved additive agents for copperelectrodeposition electrolytes which will improve the quality andphysical characteristics of the cathode electrodeposits in theelectrorefining of copper.

An additional object is to provide a new and improved combination ofadditive agents for use in electrodepositing copper from an aqueouselectrolyte which will control the deposition of copper and increasecathode polarization and thus provide electrolytically pure cathodecopper which is smooth, dense and substantially nodule-free.

Additional objects if not specifically set forth herein will be readilyapparent to those skilled in the art from the following detaileddescription of the invention.

In general, the method of this invention involves a procedure wherebyvery pure cathode copper is obtained by electrodeposition techniques andwhereby the formation of nodules or trees on the cathode is essentiallyeliminated. These results are achieved by adding to a standard acidcopper electrolyte solution containing a source of copper ions and asource of hydrogen ions, additive agents comprising cation activeorganic nitrogen compounds and lignosulfonate materials We have foundthat the resulting solution when employed as the electrolyte in theelectrodeposition of copper will provide cathode copper deposits ofimproved quality-smooth, dense and relatively free of protrusions.

More specifically, we have found that the use of cation active organicnitrogen compound selected from the group consisting of conventionalwater soluble cation active quaternary ammonium compounds and highmolecular weight polyethylene amines in conjunction with alignosulfonate material as an additive agent in copper electrodepositionbaths will produce a dense, very uniform deposit of copper, free ofprotrusions. This discovery of the advantages achieved with the conjointuse of these nitrogen compounds and lignosulfonates was surprising andhighly unexpected since a synergistic effect is displayed. The additionof these nitrogen compounds alone in copper electrodeposition bathsproduced a rough cathode deposit with voluminous growth totallyunsuitable for the electrorefining of copper. Lignosulfonate materialsadded alone to electrodeposition baths produce a rough cathode depositwith heavy nodules. However, with conjoint use of the nitrogen compoundsand lignosulfonates, an outstandingly better copper deposit was producedwhich was smooth, dense and essentially nodule free.

The quaternary ammonium salts to be employed herein may be representedby the following structural formula:

wherein R, R R and R are independently selected from the groupconsisting of alkyl and aryl radicals con taining from 1 to 20 carbonatoms, at least one of the R, R R and R must contain a minimum of 8carbon atoms, and A- is an inconsequential anion such as Cl, Br: OH andthe like. Typical quaternary ammonium salts of this class are:

methyldodecyl-benzyl trimethyl ammonium chloride methyldodecyl xylylenebis (trimethyl ammonium chloride) n-alkyl (C14, C C dimethyl benzylammonium chloride p-diisobutyl phenoxy ethoxy benzyl ammonium chlorideethyl hexadecyl dimethyl ammonium bromide diisobutyl-cresoxy-ethoxyethyl dimethyl benzyl ammonium chloride (or hydroxide) soya trimethylammonium chloride 1 di-polyoxyethylene stearyl methyl ammonium chlorideoctadecyl trimethyl ammonium chloride coco trimethylquaternary ammoniumchloride di-hydrogenated tallow dimethyl quaternary ammonium chloridecottonseed trimethyl quaternary ammonium chloride In the above listingof quaternary amomnium salts which may suitably be employed in thepresent invention, it is to be understood that by the radical coco ismeant mixed alkyl groups derived from coconut oil and comprisingessentially a mixture of saturated C C C C and C carbon length chainsand predominating in C By the cottonseed and soya radicals are meantmixed alkyl groups derived from cottonseed oil and soybean oilrespectively and comprising in each case mixtures of essentiallyunsaturated alkyl groups predominating in C carbon length cahins. Bydihydrogenated tallow is meant mixed alkyl groups comprising essentiallya mixture of saturated C and C carbon length chains.

The polyethylene amines to be employed herein are high molecular weightpolyethylene polyamines (also known as polyethylene imines) and may berepresented by the following structural formula:

The polyethylene polyamines to be utilized herein may be characterizedas having relative viscosities of at least 1.25 (measured in aqueoussolution at C. in comparison with water using a No. 100 Cannon-Fenskeviscometer) with a preferred range of from about 1.25 to about 3.00.

The lignosulfonate component of the additive agent can belignosulfonate-containing residue from the acid sulfite pulping of woodeither in crude form containing wood sugars or in substantiallysugar-free refined form, for example, as prepared by the processdescribed in U.S. Pat. No. 3,271,382. In the acid sulfite pulpingprocess, a lignocellulose material such as wood is generally cooked in asolution of sulfurous acid, part of the sulfurous acid being combined asbisulfite. The cation assosciated with the bisulfite ion is generallyknown as the pulping base. Pulping base cations normally used includesodium, calcium, ammonium, magnesium and the like. In acid sulfitepulping of conifer woods, the spent cooking liquors, irrespective of thebase used contain approximately 65% lignosulfonates, 25% wood sugars and10% inorganic salts and miscellaneous lay-products. For use inpracticing this invention, the spent sulfite liquors may be used as suchbut for economic purposes, the liquor will usually be concentrated to atleast about 40-50% concentration. More conveniently, such concentratedliquors would be dried to form water-soluble powders, to facilitateshipment and storage, by a suitable drying process such as spray drying,drum drying and the like. As used herein, the term lignosulfonate coversboth dried liquor solids and never-dried spent sulfite liquors.

The concentration of additive agent to be introduced into any givenelectrofining bath will vary considerably depending on such factors asthe impurities from the impure copper anode present in the electrolyte,the composition of the electrolyte, the temperature of the electrolyte,the current density and the like. However, generally, when a quaternaryammonium compound is used in conjunction with a lignosulfonate material,the ammonium compound and the lignosulfonate should be added separatelyto the standard acid copper electrolyte in amounts sufficient to provideconcentrations therein of from about 0.5 to about 10 milligrams ammoniumcompound and about -100 milligrams of lignosulfonate per liter ofelectrolyte, and more preferably about 0.6-1.8 mg. ammonium compound andabout 50 mg. lignosulfonate per liter of electrolyte. When apolyethylene amine is used in conjunction with a lignosulfonate materialit is usually preferred to prepare an aqueous solution of bothcomponents in the ratio of about 1 part polyethylene amine to about 250parts lignosulfonate and then dried to form a convenient condensatepowder. This condensate powder can then be dissolved in an acid copperelectrolyte in a sufficient amount to provide a concentration of about0.1 to about 0.3 mg. polyethylene amine and about 30- 100 mg.lignosulfonate per liter of electrolyte, and more preferably about0.18-0.20 mg. polyethylene amine and mg. lignosulfonate per liter ofelectrolyte.

In a preferred embodiment of the present invention, the lignosulfonatecompone of the additive agent should be introduced into the electrolytein a concentration about 20 to times that of the quaternary ammoniumcompound when that component is employed in conjunction with thelignosulfonate, and about 250 times that of the high molecular weightpolyethylene polya'mine when such an amine is a component of theadditive agent.

The following examples are set forth for the purpose of illustrationonly and are not intended to be construed as being limitative in anyrespect.

EXAMPLE I A series of copper electrodepositiontests were conducted todetermine the effectiveness of the additive agents of the presentinvention. The tests were conducted under the followingelectrodeposition conditions which were held constant for all thesamples tested:

Temperature C 30 Time, hours 47 Cathode current, density, amps persquare foot 17 Agitation, cycles per minute 40 Plating area, squareinches 5.2

The electrolytic apparatus was set up in the same manner for each sampletested. For each sample to be tested, a 32 oz. jar was utilized. Thejars were placed in a constant temperature bath. Each jar was equippedwith holders for tWo anodes and a cathode, a vertical reciprocatingstirring device and a D.C. regulated current supply. The two anodes werepositioned one on each side of the oathode and each anode was spaced oneinch from the cathode. Prior to testing, the copper anodes and thecathodes were washed 24 hours in carbon tetrachloride for degreasing andthe cathodes were pickled one hour in a 5% sulfuric acid chromergesolution. The copper sheet used was electrolytic refined copper.

The basic electrolyte introduced into each of the jars was prepared fromBakers Analytical Grade cu ric sulfate pentahydrate g./l.), C. P.sulfuric acid (125 g./l.) and hydrochloric acid (10 mg/l.). Theparticular additive agent under test was added to the electrolyte in agiven jar and the effect of the additive agent on the electrodepositionof copper was determined by visual observation of the plating at thecathode. The results of this testing are tabulated in the followingtable:

Amount Description of reof additive suiting copper agent eleetrodepesitat Additive agent employed (mg/l.) the cathode Control None Heavynodules,

treed on surface. 'lcst Number:

1 Sodium-base spent sulfite liquor solids 50 Heavy nodules,

gut less than cenr 2 Di-isobuty1 crcsoxy ethoxy ethyl dimethyl benzylanuno- 0.6 Heavy nodules.

nium chloride.

5 Di-isobutyl-cresoxyethoxy-ethyl dinlethyl benzyl ammonium chloride.

Di-isobutyl-eresoxy-ethoxy-ethyl diinethyl henzyl ammonium chloride. 7Sodium-base spent sulfite liquor solids {Sodiulmbase spent sulfiteliquor solids 50 Smooth, only 1 or U. 6 2 small nodules.

30 Heavy nodules,

more than test No. 1. 1.0 Heavy nodules.

30 Smooth, slightly 0.8 rougher than test No. 3. 00 Very similar toAmount Description of reof additive sulting copper agent eleetrodepositat Additive agent employed (mg/1.) the cathode Sodium-base spent sulfiteliquor solids 90 }Similar to test 8 Di-isobugyll-ergsoxy-ethoxy-ethyldimethyl benzyl ammo- 0.8 N o. 3.

mumc on e. 9 Dihhlydmgenated tallow dimethyl quaternary ammonium 0.6Heavy nodules.

o Ol'l e. Sodium-base spent sulfite liquor solids 50 10{Di-lhIydrmenated tallow dimethyl quaternary ammonium 0.6 }very smallnodules c l Oll e. 11 Di hhlydiiigenated tallow dimethyl quaternaryammonium 2.0 Heavy nodules.

c on e. Sodium-base spent sulfite liquor solids 50 Ivory small nod ules,12 Di-lhlyd ggenated tallow dimethyl quaternary ammonium 2.0 I less thantest No. l.

c 1 on e. 13 Cottonseed trimethyl and dicoco dimethyl quaternary am- 1.4Similar to test N o.

monium chlorides. 1. Sodium-base spent sulfite liquor solids 2.0 ]Nonodules, small 14 Cottonseed giirmthyl and dlcoco dimethyl quaternaryam- 1.4 I corner trees.

moniumc on cs. 15 Stearyl trimethyl quaternary ammonium chloride 0.8Sufipotirer than test 0. Sodium-base spent sulfite liquor solids 5O 16"{Stcaryl trimethyl quaternary ammonium chloride 0.8 nodules or flees 17Cocotrimethyl quaternary ammonium chloride- 0.8 HGaV3;1110gl111l9S,t t

roug er an es d t fi d No. l. So ium-base spen sul te liquor soli s 5018 {Cocotrimethyl quaternary ammonium chloride 0.8 ively small nodules19 Cottonseed trimethyl quaternary ammonium chloride 0.8 Heavy;notdugesi Slml ar 0 es s d b t 1n 1 l d 0 0 iumase spen su te iquor sois 5 2O "{Cottonseed trimethyl quaternary ammonium chloride 0.8 iverysmall nodules 21-.. Calcium-base spent sulfite liquor solids 50 Hieavytll110d1t11e:,N

ess an es 0. 1. 22 Di-hydrogenated tallow dimethyl quaternary ammonium1.5 Rough, similar to C elhloridie). t m 1 nd 50 test No. 1.

aciumase spen su te iquor so s 23 {Di-Il111ydrggenated tallow dimethylquaternary ammonium 1.5 ivery Small nodules c on e. Calcium-hase spentsulfite liquor solids. 50 }No nodules, small 24 Cottonseed trlmethyl anddieoco dimethyl quaternary am- 1.4 trees.

monium chlorides.

In the above described testing the additive agents employed werelignosulfonate materials and quaternary ammonium compounds. Thelignosulfonate materials employed in the instant testing were spentsulfite liquors from sodium and calcium acid sulfite pulping ofpredominantly hemlock wood which were concentrated and then spray driedwithout neutralization. However, as will be recognized by those skilledin the art, other lignosulfonate materials could be employed herein withequally outstanding results.

The weight of copper transferred was measured in each of the tests andwas very consistent at from about 33 to about 33.5 grams, whichapproximates 100% efiiciency at 600 ma. for 47 hours. Any variations inthe weight of copper deposited, which was very small, could not becorrelated with the additive used.

The results of the above tabulated testing clearly illustrate thesuperior properties of the additive agents of the present invention toimprove the physical characteristics of the cathode deposits in theelectrodeposition of copper. When lignosulfonate materials were employedin conjunction with a quaternary ammonium compound as the additiveagents in copper electrodeposition baths, the copper electrodepositswere uniformly smooth and essentially free of protrusions or nodules.The test results, also, clearly indicate the unexpected synergisticeffect attained by the conjoint use of these materials as additiveagents in reducing tree growth and nodular formation in theelectrodeposition of copper.

EXAMPLE II Employing the experimental apparatus and procedures ofExample I (except that the deposition was carried out over a period ofhours in the instant testing), the

effect of the conjoint use of polyethylene amines and lignosulfonatematerials as additive agents in electrodeposition of copper wasinvestigated.

The polyethylene polyamines to be tested were prepared from commerciallyavailable low molecular weight polyethylene amines by condensationpolymerization reaction with ethylene chloride. One such amine wasprepared by reacting equal volumes of ethylene chloride andtetraethylene pentamine for 6 hours in a steam bath and is hereinafterreferred to as Amine No. 1. Another amine was prepared by reacting equalvolumes of ethylene chloride and diethylene triamine for 6 hours in asteam bath this product is hereinafter referred to as Amine No. 2.Additionally, a commercially available polyethylene amine (Union CarbideCorporation) having an average molecular weight of 1800 was employed andis referred to hereinafter as Amine No. 3.

Characteristics of the above prepared polyethylene polyamines were asfollows:

Amine No. Relative viscosity 1 1 1.60

No. Cannon-Fenske Vise0meter-Ratio of flow time of 10% aqueous solutionvs. water at 25 C.

The lignosulfonate material employed herein was spent sulfite liquorfrom soda acid sulfite pulping of predominantly hemlock wood which wasconcentrated and then spray dried without neutralizers. As will berecognized by those skilled in the art, other lignosulfonate materialscould also have been used herein.

The results of the tests which were conducted employing the aboveidentified materials, as determined by visual TABLE II Amount ofadditive Description of resulting copper Additive agent agentelectrodeposit at employed (mg/l.) the cathode Control N Heavy modules.Test number:

1. Sodium-base spent 50 Heavy nodules,

sulfite liquor solids. less than control. 2--. Amine No. 1 O. 3 Bushy.

Sodium-base spent 50 Smooth, very 3. sulfite liquor solids. smallnodules.

Amine No. 1 0.3 4 Amino No.2 0.3 Bushy.

Sodium-base spent 50 Smooth, very sulfite liquor solids. small nodules.

Amine No. 2 0.3 6. Amine No. 3 0.18 Heavy trees,

striated. Sodium-base spent 50 7.. sulfite liquor solids. No nodules.

Amine No. 3 0. 18

The results of the above tabulated testing clearly illustrate thesuperior properties of the additive agents of the present invention toimprove the physical characteristics of the cathode deposits in theeelctrodeposition of copper. When lignosulfonate materials were employedin conjunction with polyethylene amines as the additive agents in copperelectrodeposition baths, the copper electrodeposits were uniformlysmooth and essentially free of protrusions or nodules. The test results,also, clearly indicate the unexpected synergistic effect attained by theconjoint use of these materials as additive agents in reducing treegrowth and nodular formation in the electrodeposition of copper.

Obviously, many modifications and variations of the invention ashereinbefore set forth may be made Without departing from the spirit andscope thereof, therefore, only such limitations should be imposed as areindicated in the appended claims.

We claim:

1. An aqueous acidic copper electrodeposition electrolyte comprising asits essential ingredients a source of copper ions, a source of hydrogenions and an amount of an additive agent effective to provide anelectrolyte which produces copper electrodeposits which are smooth,dense and essentially free of protrusions, said additive agentcomprising a lignosulfonate material and a cation active organicnitrogen compound selected from the group consisting of polyethyleneamines and quaternary ammonium compounds having the general formula:

wherein R, R R and R are independently selected from the groupconsisting of alkyl and aryl radicals containing from 1 to 20 carbonatoms, at least one of R, R R and R must contain a minimum of 8 carbonatoms, and A" is an anion, and mixtures thereof.

2. The electrolyte of claim 1 wherein the cation active organic nitrogencompound is a polyethylene polyamine.

3. The electrolyte of claim 2 wherein the polyethylene polyamine has arelative viscosity of at least 1.25 measured in 10% aqueous solution atC. in comparison with water.

4. The electrolyte of claim 2 wherein the concentration of polyethylenepolyamine is from about 0.1 to about 0.3 mg./l. and the concentration oflignosulfonate material is from about 30 to about mg./l.

5. The electrolyte of claim 1 wherein the lignosulfonate material is thelignosulfonate-containing residue from the acid sulfite pulping of wood.

6. The electrolyte of claim 1 wherein the concentration of quaternaryammonium compound is from about 0.5 to about 10 mg./l. and theconcentration of lignosulfonate material is from about 30 to about 100mg./l.

7. A combination of additive agents for copper electrodepositionelectrolytes which improve the quality and physical characteristics ofthe copper electrodeposits comprising: a mixture of a cation activeorganic nitrogen compound selected from the group consisting ofquaternary ammonium compounds, polyethylene amines and mixtures thereof,and a lignosulfonate material; said quaternary ammonium compounds havingthe general formula:

wherein R, R R and R are independently selected from the groupconsisting of alkyl and aryl radicals containing from 1 to 20 carbonatoms, at least one of R, R R and R must contain a minimum of 8 carbonatoms, and A is an anion.

8. The combination of additive agents of claim 7 wherein the cationactive organic nitrogen compound is a polyethylene polyamine.

9. The combination of additive agents of claim 8 wherein the highmolecular weight polyethylene polyamine has a relative viscosity of atleast 1.25 measured in 10% aqueous solution at 25 C. in comparison withWater.

10. The combination of additive agents of claim 7 wherein thelignosulfonate material is the lignosulfonatecontaining residue from theacid sulfite pulping of wood.

11. In the method of electrodepositing copper from an aqueous acidicelectrolyte, the electrolyte comprising as its essential ingredients asource of copper ions and a source of hydrogen ions, the stepscomprising adding to the electrolyte in an amount effective to providean electrolyte which produces copper electrodeposits which are smooth,dense and essentially free of protrusions, a cation active organicnitrogen compound selected from the group consisting of quaternaryammonium compounds having the general formula:

l R -lTI-R; A-

wherein R, R R and R are independently selected from the groupconsisting of alkyl and aryl radicals containing from 1 to 20 carbonatoms, at least one of R, R R and R must contain a minimum of 8 carbonatoms, and A is an anion, polyethylene amines and mixtures thereof, inconjunction with a lignosulfonate material; and then passing an electriccurrent from an anode through the electrolyte to a cathode to depositcopper thereon.

12. The method of claim 11 wherein the cation active organic nitrogencompound added to the electrolyte comprises a polyethylene polyamine.

13. The method of claim 12 wherein the polyethylene polyamine has arelative viscosity of at least 1.25 measured in 10% aqueous solution at25 C. in comparison with water.

14. The method of claim 11 wherein the lignosulfonate material added tothe electrolyte comprises a lignosulfonate-containing residue from theacid sulfite pulping of wood.

9 15. The method of claim 11 wherein the cation active organic nitrogencompound is added in an amount of about 0.1 to about 10 mg./l. and thelignosulfonate material is added in an amount of about 30 to about 100mg./l.

References Cited UNITED STATES PATENTS 10 2,805,194 9/1957 Beaver et al.204-52 2,853,444 9/1958 Pye et a1. 204108 FOREIGN PATENTS 583,003 12/1946 Great Britain 204-106 204DIG 2 US. Cl. X.R.

